The architecture of a monolithic, dual axis, low cost surface micromachined [1] accelerometer is described, initial characterization results are presented, and issues surrounding the intended application are discussed. While the fabrication technology for the integrated mechanical sensor and electronics is essentially the same as that which supported earlier single axis products [2] [3] [4] [5] [6], a fundamentally different circuit architecture leads to much more compact and higher performance second generation devices.
Compared to available bulk micromachined accelerometer sensors, surface micro-machined sensors are typically 20X smaller (0.58 mm x 0.66 mm) and have a natural axis of sensitivity (in the plane of the chip) that facilitates multi-axis sensing. The dual axis surface micromachined accelerometer shares on-chip BiMOS circuit and packaging overhead between axes, and vividly illustrates the cost reduction potential of a fully integrated single chip approach for multi-axis sensing.
The dual axis accelerometer has been specifically developed for automotive safety systems that provide both front and side airbag protection. Features include low pass filtering, digitally activated self test, a low all-inclusive sensitivity tolerance (over supply, temperature, and life), and a surface-mountable 14 lead package.
